Method of making cores for electrical apparatus



June 1937- R. M. PFALZGRAFF 2,083,395

METHOD OF MAKING CORES FOR ELECTRICAL APPARATUS Filed Aug. 14, 1955 I g I I I u 2/ 21 k Invenfiop Ross M. Pfalzgmff HIS Attowneg.

Patented June 8, 1937 PATENT OFFICE METHOD OF MAKING CORES FOR ELEG TRICAL APPARATUS Ross M. Pfalzgratf, lLynn, Mass, assigrior to General Electric (Company, a corporation of New York Application August it, 1935, denial No, 36,103

1 Claim.

My invention relates'to a method of making cores for electrical apparatus of the type including a laminated core structure having a frame cast thereon.

In making cores for electrical apparatus in which the laminations are retained in assembled relation by a metal frame cast about the periphery of the laminations, dimculty is encountered in obtaining satisfactory castings, as the frames are m likely to crack unless some provision is made to allow for the shrinkage of the metal frame during cooling.

An object of my invention is to provide an improved core for electrical apparatus comprising 15 assembled laminations secured in a metal frame cast about the edge of the laminations and constructed in such manner as to minimize shrinlzage cracks in the cast metal.

Another object of my invention is to provide an m improved method of making a core for electrical apparatus by casting a metal frame about the edge of assembled laminations in such manner as to minimize shrinkage cracks in the cast metal. My invention will be more fully set forth in the 25 following description referring to the accompany ing drawing and the features of novelty which characterize my invention will be pointed out with particularity in the claim annexed to and forming a of this specification.

ZFor a better understanding of my invention, reference is made to the accompanying drawing, wherein Fig. l is a perspective view, partly in section, of a stator core embodying my invention; Fig. 2 is an enlarged fragmentary sectional view oi assembled laminations clamped together and illustrating the axially spread edge thereof; Fig.

3 is a sectional view of the assembled core ng to the drawing, 1 have shown my in in connection with the stationary member of a dmamdelectric machine including a lamimagnetic core structure it having a series of it providing slots it, in which any suitable windings may be placed. This core struc- 45 ture secured in a continuous thin frame ill, of iron or other metal, cast in direct contact with the entire outer edge or peripheral surface i l and with the adjacent sides 05 and it of the laminated core for clamping the laminations in assem= 5 bled relation.

in manufacturing such a stationary member, I have found that some provision must be made to allow for shrinkage of the cast frame both axially and radially to prevent the development of 55 cracks in the cast metal upon cooling. 1 assemble the laminations it and clamp them in the desired relation by annular clamping rings ill having their outer periphery just beyond the base portions of the teeth l2 and extending inwardly slightly beyond the mid portion of the teeth. These clamping rings are secured together by bolts lit arranged in the slots it and out of contact with the bottom of the slots, so as to permit a certain amount of radial shrinkage on cooling of the cast frame it. The clamping pressure on the inner edge of the laminations is adjusted by tightening the nuts ill on the bolts 98, so as to cause the other edge of the laminations to spread apart axially, as illustrated in Fig. 2. This axially spread edge oi the laminations ls compressible and allows for axial shrinkage of the cast frame when it cools. around this axially spread edge and the adjacent sides of the lamlnations is arranged, as shown in Fig. 3, a mold Ell, which may be of the permanent type or or such material as molding sand, and which cooperates with upper and lower cores 26 to form the complete mold for the cast frame. This mold is supported by a iiaslr 22 and arranged between top and bottom boards 23 and 26 held together by clamps 25. The clamping rings ll are of such size that they just cover the slots ii and the use or a sand mold between these rings and the molding space provides a yieldable cushion which permits radial shrirlrage of that portion of the cast frame extending beyond the laminations. The top board 23 is provided with an opening communicating with the gate into which the metal is poured in casting the frame it. Thus, it is seen that T. provide a core structure for electrical apparatus utilizing assembled laminations retained the desired relation by a continuous metal frame cast in direct contact with edge and the adjacent sides of the laminations, and provide a method of making the same which allows for both radial and axial shrinkage of the cast frame, thereby preventing the formation of oracles in the finished product.

Although i have shown my invention in con nection with a dynamo electric machine, it is apparent that it can be used in other types of elec= tribal apparatus utilizing laminated core struc-= tures and modifications oi the embodiment of my invention illustrated and described will be an- ;carent to those skilled in the art. li desire it to be understood, therefore, that my invention is not to be limited to the particular arrangement disclosed, and if intend, in the appended claim to cover all modifications which do not from the spirit and scope of my invention.

2 aosaaos What I claim as new and desire to secure by Letters Patent of the United States is:

The method of making a core for electrical apparatus which consists of assembling a group of annular laminations having a series of slots in one edge thereof, clamping together said slotted edge by clamping rings secured by means out of contact with the bottom of said slots in said laminations to permit radial shrinkage of said laminations and under such pressure as to cause the other edge of said laminations to spread axially, forming a mold with a molding space about said spread edge of said assembled laminations and a yieldable portion of the mold between said clamping rings and said molding space, and casting a metal frame in contact with said assembled laminations in saidmolding space.

ROSS M. PFALZGRAFF. 

